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How does this work regardless? Isn't route53 a DNS system? How does it know whether a service went up/down? EDIT: To reply to myself http://docs.aws.amazon.com

• zimbatm 12y ago
  Unfortunately inside of AWS there is no other solution than to rely on DNS to update the list of IP that resolve from an address (even ELB does that). Route53 has health-checks that can update the list automatically. Uptime is entirely dependent on the TTL of those records and if the clients respects that TTL. Complementary to that it's also possible to assign reserved IPs to machines so that at least the set of IP is always the same even if the hosts get rotated. Assigning IPs to hosts is not instantaneous either and depends on an API call. Also IPs are tied to a specific region. In a real datacenter other options are possible like sharing IP addresses between multiple devices and having lower-latency failover. These aren't perfect either and have different failure scenarios.